UC San Diego

Sunscreen products contain chemicals such as oxybenzone or minerals such as titanium dioxide (TiO2) and zinc oxide (ZnO), which are a threat to marine biota and especially to coral reefs. Mineral sunscreens are being marketed as “reef-safe”; however, their impacts on marine organisms are not well understood. The aim of my thesis was to evaluate the effects of oxybenzone, TiO2, and ZnO on photophysiological properties of sea anemone Anthopleura elegantissima. This invertebrate belongs to the phylum Cnidaria and is a close relative to reef-building corals. Anemones were exposed to three environmentally relevant concentrations of oxybenzone, TiO2, and ZnO (nominally, 0.01 microgram/L, 0.1 microgram/L, and 1 microgram/L) for 21 days, followed by seven days of recovery in the absence of sunscreen ingredients. Throughout this 28-day period, measurements of fluorescence intensity and photosynthetic efficiency were taken as proxies for anemone photophysiology. The sunscreen ingredients did not seem to affect either parameter over the course of the experiment. However, analyses of seawater samples using inductively coupled plasma-mass spectrometry (ICP-MS) revealed prominent mismatches in the concentrations of TiO2 and ZnO compared to the target values, including much higher concentrations in the controls than in treatment samples. Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis failed to detect oxybenzone. Overall, the unexpectedly high TiO2 and ZnO concentrations measured in the experimental aquarium coupled with oxybenzone analysis issues prevented reaching conclusions about their potential toxicity on anemone photophysiology. These factors must be considered for future studies aiming to assess potential toxic effects of sunscreen compounds on marine life.